Commit 2e0ad552 authored Apr 20, 2018 by Alexey Dobriyan Committed by Linus Torvalds Apr 20, 2018

proc: revalidate kernel thread inodes to root:root

task_dump_owner() has the following code:

	mm = task->mm;
	if (mm) {
		if (get_dumpable(mm) != SUID_DUMP_USER) {
			uid = ...
		}
	}

Check for ->mm is buggy -- kernel thread might be borrowing mm
and inode will go to some random uid:gid pair.

Link: http://lkml.kernel.org/r/20180412220109.GA20978@avx2


Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 1e630665

fs/proc/base.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -1693,6 +1693,12 @@ void task_dump_owner(struct task_struct *task, umode_t mode,
		kuid_t uid;
		kgid_t gid;

		if (unlikely(task->flags & PF_KTHREAD)) {
		*ruid = GLOBAL_ROOT_UID;
		*rgid = GLOBAL_ROOT_GID;
		return;
		}

		/* Default to the tasks effective ownership */
		rcu_read_lock();
		cred = __task_cred(task);